Allen and Sean O'Brien are looking for the American dream, but they basically find an American nightmare. At first, they're hapless comic relief. They're so hopeless that they meant to hit Galveston and ended up near Mexico. Basically, they saw America in a magazine—but this isn't the America they wanted:
"Young Sean O'Brien could not conceal his disappointment with America." (12.83)
However, once the tears are dry, the O'Briens do learn to work on the cattle drive. This is the American dream, right? They're learning to survive on their own. How inspirational.
At least until young Sean is devoured by snakes in a river.
Devoured by snakes.
Sean's the first person to die on the cattle run, and it's shocking and tragic when it happens. Newt cries, and Sean's brother, Allen, tries to sing a song in tribute but can't finish it. Allen survives the entire book, but after so many deaths, he seems to be dried up inside.
"I need to cry, but I've got no tears. […] This goddamn country has burned up my tears." (89.108)
The Wild West isn't a romantic place for everyone.